As is well known, certain types of pitch change motors for small size variable pitch propellers utilize a ball screw and ball screw nut for controlling the position of a servo motor which in turn drives a piston operatively connected to the blades of the propeller for varying pitch. In certain designs, as for example, for the 14RF and 14SF model propellers manufacturedby the Hamilton Standard division of United Technologies Corporation, the assignee common to this patent application, the torque from the ball screw is transmitted to the torque oil transfer tube by a quill shaft that is splined to both sub-assemblies. This type of propeller is disclosed in U.S. Pat. No. 4,523,891 granted to R. A. Schwartz et al on Jun. 18, 1985 entitled "Propeller Pitch Change Actuation System" which was also assigned to the above-noted assignee and which is incorporated herein by reference.
While the propeller disclosed in the U.S. Pat. No. 4,523,891 supra, has been satisfactory, there have been instances where unacceptable rates of wear have been experienced on the ball screw spline which mates with the quill shaft. Such wear was occasioned by high vibration loads coupled with cyclic torsion loads, resulting in wear producing impact loading at a high cycle per second rate.
We have found that we can obviate this wear problem by including a damper for dissipating the vibratory loadings encountered, while also providing means for trapping the oil in the spline so as to enhance the lubrication and load carrying capacity of the components.